Contact Types (LD Code Objects)

Contacts and coils are basic elements of LD networks.

In PLCnext Engineer, they can be used in FBD/LD, NOLD, SNOLD and SFC code worksheets.

A contact copies the Boolean value from its left to its right depending on the state of the associated variable (shown above the contact). The type of the contact is represented with the symbol of its modifier. Available contact types/modifiers:

Normally open contact The Boolean value is copied from the left to the right if the state of the associated variable is TRUE.

Normally closed contact The Boolean value is copied from the left to the right if the state of the associated variable is FALSE.

Positive transition-sensing contact The positive transition-sensing contact compares the value of the associated data item during the current ladder rung evaluation to its value during the previous ladder rung evaluation. The value TRUE is copied from the left to the right when the value of the associated data item changes from FALSE to TRUE.
This object is not supported in safety-related code (SNOLD).

Negative transition-sensing contact The negative transition-sensing contact compares the value of the associated data item during the current ladder rung evaluation to its value during the previous ladder rung evaluation. The value TRUE is copied from the left to the right when the value of the associated data item changes from TRUE to FALSE.
This object is not supported in safety-related code (SNOLD).

Further Info
For a description of the objects that are common to all graphical programming languages, for example, connectors, jumps, returns etc. refer to the topic "Constants, Jumps/Labels, Returns, Connectors".

	Normally open contact	The Boolean value is copied from the left to the right if the state of the associated variable is TRUE.
	Normally closed contact	The Boolean value is copied from the left to the right if the state of the associated variable is FALSE.
	Positive transition-sensing contact	The positive transition-sensing contact compares the value of the associated data item during the current ladder rung evaluation to its value during the previous ladder rung evaluation. The value TRUE is copied from the left to the right when the value of the associated data item changes from FALSE to TRUE. This object is not supported in safety-related code (SNOLD).
	Negative transition-sensing contact	The negative transition-sensing contact compares the value of the associated data item during the current ladder rung evaluation to its value during the previous ladder rung evaluation. The value TRUE is copied from the left to the right when the value of the associated data item changes from TRUE to FALSE. This object is not supported in safety-related code (SNOLD).